Tchinda Romaric Armel Mouafo, Boudjeko Thaddée, Simao-Beaunoir Anne-Marie, Lerat Sylvain, Tsala Éric, Monga Ernest, Beaulieu Carole
Laboratory of Phytoprotection and Valorization of Plants Resources, Biotechnology Centre-Nkolbisson.
Microbes Environ. 2016;31(1):56-62. doi: 10.1264/jsme2.ME15146. Epub 2016 Mar 5.
Vascular plants are commonly colonized by endophytic actinobacteria. However, very little is known about the relationship between these microorganisms and cacao fruits. In order to determine the physiological and taxonomic relationships between the members of this community, actinobacteria were isolated from cacao fruits and seeds. Among the 49 isolates recovered, 11 morphologically distinct isolates were selected for further characterization. Sequencing of the 16S rRNA gene allowed the partition of the selected isolates into three phylogenetic clades. Most of the selected endophytic isolates belonged to the Streptomyces violaceusniger clade. Physiological characterization was carried out and a similarity index was used to cluster the isolates. However, clustering based on physiological properties did not match phylogenetic lineages. Isolates were also characterized for traits commonly associated with plant growth-promoting bacteria, including antibiosis and auxin biosynthesis. All isolates exhibited resistance to geldanamycin, whereas only two isolates were shown to produce this antibiotic. Endophytes were inoculated on radish seedlings and most isolates were found to possess plant growth-promoting abilities. These endophytic actinobacteria inhibited the growth of various plant pathogenic fungi and/or bacteria. The present study showed that S. violaceusniger clade members represent a significant part of the actinobacterial community living as endophytes in cacao fruits and seeds. While several members of this clade are known to be geldanamycin producers and efficient biocontrol agents of plant diseases, we herein established the endophytic lifestyle of some of these microorganisms, demonstrating their potential as plant health agents.
维管植物通常会被内生放线菌定殖。然而，对于这些微生物与可可果实之间的关系，我们知之甚少。为了确定这个群落成员之间的生理和分类关系，从可可果实和种子中分离出了放线菌。在回收的49个分离株中，选择了11个形态不同的分离株进行进一步鉴定。16S rRNA基因测序使所选分离株被分为三个系统发育分支。大多数所选的内生分离株属于紫色黑链霉菌分支。进行了生理特性鉴定，并使用相似性指数对分离株进行聚类。然而，基于生理特性的聚类与系统发育谱系不匹配。还对分离株进行了与促进植物生长的细菌相关的常见性状鉴定，包括抗菌作用和生长素生物合成。所有分离株都对格尔德霉素有抗性，而只有两个分离株被证明能产生这种抗生素。将内生菌接种到萝卜幼苗上，发现大多数分离株具有促进植物生长的能力。这些内生放线菌抑制了各种植物病原真菌和/或细菌的生长。本研究表明，紫色黑链霉菌分支成员是生活在可可果实和种子中的内生放线菌群落的重要组成部分。虽然已知该分支的几个成员是格尔德霉素生产者和植物病害的有效生物防治剂，但我们在此确定了其中一些微生物的内生生活方式，证明了它们作为植物健康剂的潜力。
